1. Field
The present disclosure relates generally to ultrasound testing and, in particular, to ultrasound testing of composite structures. Still more particularly, the present disclosure relates to a system and method for testing a composite structure using a laser ultrasound testing system.
2. Background
A composite structure, as used herein, may be any structure comprised of at least one composite material. The composite material may include a matrix material and a reinforcement material. Composite structures may be inspected using different types of testing systems. A laser ultrasound testing (UT) system is an example of one type of testing system that may be used to test a composite structure for undesired inconsistencies. Laser ultrasound testing allows a composite structure to be tested without the testing system physically contacting the composite structure.
Typically, a laser ultrasound testing system uses a pulsed laser beam to generate ultrasonic waves in a composite structure. A pulsed laser beam is a beam formed by pulses of laser energy that are emitted at some selected pulse repetition rate. The laser ultrasound testing system is capable of detecting these ultrasonic waves and using the detected ultrasonic waves to generate data about the composite structure. This data may be used to identify information about the composite structure such as, for example, without limitation, a thickness of the composite structure, a material composition of the composite structure, an indication of whether any undesired inconsistencies are present on and/or in the composite structure, and/or other types of information.
With some currently available laser ultrasound testing systems, a gas laser source is used to generate a pulsed laser beam that has a spot size of about five millimeters (mm). The spot size is the size of the area on the surface of a composite structure that is illuminated by the laser beam. In some situations, a spot size of about five millimeters may not be small enough to allow a finer level of detail to be characterized with respect to the composite structure.
Further, with some currently available laser ultrasound testing systems, the scanning rate, or rate at which the pulsed laser beam may be moved along the surface of the composite structure, is determined by the pulse repetition rate of the laser ultrasound testing system. Some currently available laser ultrasound testing systems may be unable to generate a pulsed laser beam with a pulse repetition rate high enough to provide a scanning rate within selected tolerances. Additionally, the size, weight, and/or cost of some currently available laser ultrasound testing systems that use gas laser sources may be greater than desired. Further, the size and/or weight of these types of laser ultrasound testing systems may require that testing be performed in an area or room that has shielding or some other type of protection. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues.